System and method for dynamic hybrid automatic repeat request (harq) enable/disable

ABSTRACT

A system and method of increasing data throughput in a wireless communications network between a base station (BS) and one or more mobile stations (MS) includes establishing a service flow (SF) and initially enabling a hybrid automated repeat request (HARQ) protocol; determining, at a particular time, the measure of quality of the communications channel; comparing the determined measure of quality with a predetermined channel quality threshold; and selectively disabling the HARQ protocol based upon a first comparison result while continuing the SF between the BS and MS. In other aspects, after selectively disabling the HARQ protocol, the method further includes determining that the time-varying measure of quality of the communications channel has deteriorated below the predetermined channel quality threshold; and selectively re-enabling the HARQ protocol in the established SF.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is related to co-pending U.S. patent application Ser.No. ______ (Attorney Docket No. 017421-0379806) entitled “System andMethod for Hybrid Schemes of MIMO Mode Decision” and co-pending U.S.patent application Ser. No. ______ (Attorney Docket No. 017421-0379807)entitled “System and Method for Adaptive Control of an AveragingParameter”, both of which are concurrently filed herewith and both ofwhich are hereby incorporated by reference herein in their entirety.

BACKGROUND

In one or more embodiments, this disclosure is directed to a system andmethod useful for generating and processing automatic repeat request(ARQ) signals in wireless communications networks. In particular, thisapplication is directed to a system and method for dynamic control ofARQ signals in wireless communications networks that involve a hybridapproach over conventionally known signal protocols and communicationsstandards. Even more particularly, this application is directed to asystem and method for improving communication channel performance by thedynamic control of hybrid ARQ (HARQ) in Broadband Wireless Access (BWA)communications systems based upon monitoring and selectively respondingto changing communication channel conditions to improve data throughputand/or the number of users that may access the communications network.

As a result of the demand for longer-range wireless networking, the IEEEStandard 802.16 was developed. The IEEE 802.16 standard is oftenreferred to as Wireless Metropolitan Area Network (WiMAX), “mobileWiMax”, or less commonly as WirelessMAN or the Air Interface Standard.This standard provides a specification for fixed broadband wirelessmetropolitan access networks (“MANs”) that use a point-to-multipointarchitecture. Such communications can be implemented, for example, usingorthogonal frequency division multiplexing (“OFDM”) communication. OFDMcommunication uses a spread spectrum technique distributes the data overa large number of carriers that are spaced apart at precise frequencies.This spacing provides the “orthogonality” that prevents the demodulatorsfrom seeing frequencies other than their own. Expected data throughputfor a typical WiMAX network is 45 MBits/sec per channel. The 802.16estandard defines a media access control (“MAC”) layer (OSI level 2,sometimes referred to as the “Radio Link Control” or “RLC” layer) thatsupports multiple physical layer specifications customized for thefrequency band of use and their associated regulations. This MAC layeruses protocols to ensure that signals sent from different stations usingthe same channel do not interfere with each other or “collide”.

The IEEE 802.16 system architecture, for example, consists of twological entities, the Base Station (BS) and the Subscriber Station (SS).Both the BS and SS have instances of the IEEE 802.16 MAC and PhysicalLayer 1 (PHY), in addition to other support functions. However, specificfunctions performed by the MAC or PHY differ depending on whether it isa BS or SS, and the IEEE 802.16 standard defines the BS- and SS-specificbehavior in detail. The term SS is applied in a fixed context, while theMS is used in a mobile environment, as introduced by IEEE Std 802.16e.

In Point-to-Point (PtP) and Point-to-Multipoint (PMP) networks, the BSand SS are in a master-slave relationship, where the SS must obey allmedium access rules enforced by the BS. The mobile station (MS) definedin the IEEE 802.16 mobility extension (IEEE Std 802.16e) requiressupport for additional SS-specific functions such as mobilitymanagement, handoff, and power conservation. In this disclosure, theterm “SS” is intended to not only include fixed or relatively immobileterminal equipment, but to also include MS functionality of mobile userterminal equipment, unless specifically stated otherwise. One of thebasic differences between the BS and SS in a PMP network configurationis that the BS, which acts as a centralized controller and a centralizeddistribution/aggregation point, has to coordinate transmissions to/frommultiple SSs, whereas the SS need only to deal with one BS. All trafficoriginating from an SS, including all SS-to-SS traffic must go throughthe BS. Therefore, in a typical IEEE 802.16 system, the BS has to haveadditional processing and buffering (i.e., memory) capability incomparison to a typical SS to support a reasonable number of SSs.

The functions of the BS and SS depend on the operation mode, namely, PMPor mesh. The functions of the Base Station include:

-   -   Enforce MAC and physical parameters such as frame size.    -   Perform bandwidth allocation for downlink and uplink traffic per        SS.    -   Perform centralized Quality of Service (QoS) scheduling based on        the QoS parameters configured by the management system and the        active bandwidth requests received from the SS.    -   Transmit/receive data and control information to/from one or        more SSs.    -   Provide SS support services like ranging, clock synchronization,        power control and handover.

The functions of the Subscriber Station or Mobile Station include:

-   -   Identify the BS, acquire physical synchronization, obtain MAC        parameters and join the network.    -   Establish basic connectivity, setup data and management        connections and negotiate parameters as needed.    -   Generate bandwidth requests for connections.    -   Receive all scheduling and channel information broadcasted and        proceed according to the medium access rules provided by the BS,        unless in sleep mode.    -   Perform specific functions for mobility management, handover and        power conservation.

Various methods and metrics have been developed to indicate the channelcondition or Channel Quality Indicator (CQI). Exemplary metrics includea Physical Carrier to Interference plus Noise Ratio (PCINR), a ReceivedSignal Strength Indicator (RSSI), an ACK/NACK ratio that indicates aproportion of successful data transmissions to unsuccessful transmission(thereby indicating channel stability), PCINR Standard Deviation (SD)that may indicate Doppler and fading effects that result from movementof the MS, and other indicators. These indicators may be generated atthe MS or SS and transmitted to the BS by known techniques ofrepresenting the CQI. The BS may receive the channel conditionindicators, e.g., CQI, and attempt to adjust communication in responseto changes to the channel condition. For example, the BS may performdownload link adaption such as, for example, selecting an appropriateModulation Coding Scheme (MCS) according to the channel condition inresponse to various changes to the channel condition. Knowing currentand accurate channel condition information may enhance the ability ofthe BS to respond to changes to the channel condition. Current systems,however, are not configured to make use of such channel conditioninformation to change various signaling parameters, particularly in anautomated fashion.

Manual selective implementation of a well-known error control techniquefor data transmission, Automatic repeat-request (ARQ), utilizesacknowledgments and timeouts to achieve reliable data transmission. ARQacknowledgments are messages sent by the receiver to the transmitter toindicate that the receiver correctly received an information unit.Timeouts are reasonable points in time after the sender transmits theinformation unit. The sender usually re-transmits the information unitif it does not receive an acknowledgment before the timeout. Itcontinues to re-transmit the information unit until it either receivesan acknowledgment from the receiver or exceeds a predefined number ofre-transmission attempts. FIG. 2 depicts a notional timeline and messageflow for packet transmission/acknowledgement and retransmission in caseswhere no acknowledgement (negative acknowledgement or NACK) of atransmitted packet is received.

Conventional types of ARQ protocols include “stop-and-wait ARQ”,“go-back-N ARQ” and “selective repeat ARQ”. These protocols typicallyreside in the Data Link or Transport Layer 2 of the OSI 7-layer model.

Conventional Hybrid ARQ (HARQ) is a commonly used extension of the ARQerror control method that exhibits better performance, particularly overwireless channels, but at the cost of increased implementationcomplexity. HARQ is used in several conventional wireless communicationssystems including High-Speed Downlink Packet Access (HSDPA) andHigh-Speed Uplink Packet Access (HSUPA) (i.e., third generation mobiletelephony communications protocols in the High-Speed Packet Access(HSPA) family) which allow networks based on Universal MobileTelecommunications System (UMTS) to have higher data transfer speeds andcapacity on downlink and uplink, respectively, for mobile phone networksusing the UMTS.

HARQ has also been used in the currently implemented IEEE 802.16-2005standard for mobile broadband wireless access, i.e., “mobile WiMAX”.Presently, HARQ provides an important technology for increasing datatransmission reliability and data throughput in mobile communicationsystems. Specifically, in the WiMax implementation, HARQ refers to acombination of ARQ and PHY layer reception techniques like Forward ErrorCorrection (FEC) and signal combining techniques. Different from ARQoperating solely at the MAC layer, HARQ allows the receiver to performsoft-combining of retransmitted packets and therefore may provide somemeasure of improvement in spectral efficiency. There are two well-knownHARQ techniques: the first known as Incremental Redundancy (IR) and thesecond known as chase combining, discussed further below.

HARQ is an important technique for link adaptation, and makes aggressivemodulation and coding schemes (MCS) decisions possible, e.g., the use ofOFDM. Thus, the use of HARQ can result in considerable increased datathroughput, and/or can enable more users to access the network. In HARQ,the transmitter and the receiver cooperate on an information unit (HARQsub burst, burst, packet or block) level. The receiver is capable ofindicating successful (via ACKs) or unsuccessful (via NACKs) receptionof the last transmitted information unit or block. The transmittercomprises several parallel HARQ sub processors (e.g., in 802.16ereferred to as HARQ sub-channels), each of which performs operations oftransmitting user information units, receiving ACK/NACK information orother ACK indications in response, and performing either aretransmission when needed or transmitting the next information units.The ACK indication may be direct whereby a specific ACK or NACKindication is sent. In HARQ, the receiver takes advantage of anyprevious retransmissions by decoding the information unit or block basedon information gathered from all the retransmissions of the sameinformation unit or block, thus improving overall performance of thecommunications link.

In IEEE 802.16e, HARQ schemes are optional parts of the MAC layer, andcan currently only be enabled on a per-terminal per connection basis,when a Service Flow (SF) is established between the BS and SS. Theper-terminal HARQ and associated parameters are specified and negotiatedduring the initialization procedure, and currently cannot be altered foran established SF. In other words, once HARQ is enabled, it may not bechanged during the duration of the particular SF.

As mentioned above, Chase Combining is used in the current WiMAXprofile, although IEEE 802.16e also supports IR. A SS may support IR,while a MS may support either Chase Combining or IR. For IR, the PHYlayer will encode the HARQ packet generating several versions of encodedsubpackets. Each subpacket is uniquely identified using a subpacketidentifier (SPID). For Chase Combining, the PHY layer encodes the HARQpacket generating only one version of the encoded packet. As a result,no SPID is required for Chase Combining HARQ Chase Combining requiresall retransmissions to send the exact same information and to use theoriginal modulation-coding scheme (i.e. waveform). Note that HARQretransmissions are asynchronous, in the sense that all HARQ burstsundergo opportunistic scheduling. The maximum number of retransmissionsis determined by target residual Packet Error Rate (PER). Typically thenumber of HARQ retransmissions is set to four, for a PER of 1×10⁻⁴ (thisis the case for IR as well).

A benefit of employing HARQ is that it can be used to mitigate theeffects of channel and interference fluctuation. HARQ provides animprovement in performance due to the SNR improvement derived from theenergy and time diversity gain achieved by (1) combining retransmittedpackets with previous erroneously decoded packets and/or (2) usingIncremental Redundancy (IR) to realize additional coding gain.

Using WiMAX as an example, a resource region for HARQ ACK channels isallocated using the HARQ ACK region allocation Information Element (IE).This resource region may include one or more ACK channels for HARQsupport-enabled MSs, e.g., ACKCH 150 n in FIG. 1. The uplink (UL) ACKchannel occupies half a slot in the HARQ ACK channel region, which mayoverride the fast feedback region. This UL ACK channel is assignedimplicitly to each HARQ-enabled burst, according to the order of theHARQ-enabled downlink (DL) bursts in the DL-MAP. Thus, using this UL ACKchannel, SSs or MSs can quickly transmit ACK or NACK feedback for DLHARQ-enabled packet data.

HARQ may also divide into several types. In the simplest version of HARQtypes, called Type I HARQ, both Error Detection (ED) and Forward ErrorCorrection (FEC) information to each message prior to transmission. Whenthe coded data block is received, the receiver first decodes theerror-correction code. If the channel quality is sufficient, alltransmission errors should be correctable, and the receiver can obtainthe correct data block. If the channel quality is bad and not alltransmission errors can be corrected, the receiver detects thissituation using the error-detection code, the received coded data blockis discarded, and the receiver requests retransmission. The moreretransmissions that are required for successful reception, the less arethe available resources (e.g., transmission power, number of availabletransmission slots) to provide data throughput for other users.

In the more sophisticated Type II HARQ, only (1) ED bits or (2) FECinformation and ED bits are sent on a given transmission, typicallyalternating on successive transmissions. It is important to note thatdetection typically adds only a few bytes to a message, resulting in arelatively small incremental increase in message length. FEC, however,adds error correction parities, which often double or triple the messagelength. In terms of throughput, standard ARQ typically expends a fewpercent of channel capacity for reliable protection against error, whileFEC ordinarily expends half or more of all channel capacity for channelimprovement.

In Type II HARQ, the first transmission contains only data and errordetection. If it is received in error, the second transmission includesFEC parities and error detection information. If the second transmissionis received in error, error correction is attempted by combining theinformation received from both transmissions. Incorrectly received codeddata blocks are often stored in buffer memory at the receiver ratherthan discarded. When the retransmitted block is received, the two blocksare combined, using a technique known as Chase Combining, whichincreases the likelihood of correctly decoding the message.

FIG. 1 depicts the architecture of a WiMAX network implemented inaccordance with various aspects of IEEE Standard 802.16. In FIG. 1, basestation (BS) 110 may communicate with one or more MobileStations/Subscriber Stations (MS/SS) 130 a-130 n over network 120 via anassociated communication channel 140 a-140 n. In this disclosure, theterms “SS” and “MS” are used interchangeably, although it is recognizedthat MS implies the use of mobility enhancements. MS/SS 130 a-130 n maybe relatively fixed or immobile terminal equipment, or may be equipmentthat includes the mobility functions of a MS, e.g., a cell phone orlaptop computer traveling in an automobile or airplane. Various factorssuch as the existence of ambient interference around the SS or BS,movement of the SS, and other factors may degrade or otherwise alter thechannel condition of the communication channel, making the use of HARQdesirable to ensure reliable communications over channels 140 a-140 n.HARQ uplink Acknowledgement Channels (ACKCH) 150 a-150 n allow eachMS/SS 130 a-130 n to acknowledge packet receipt to the BS by use of aHARQ signal transmission over a dedicated HARQ ACK channel. AlthoughHARQ provides advantages under some channel conditions, these ACKCHchannels represent additional channel overhead that will decrease datathroughput when channel conditions are such that communication may bereliably maintained without HARQ being used. Channel Quality Indicator(CQI) channels 160 a-160 n provide a path for the MS or SS to identifythe relative quality of the communication channel to BS 110 using knowntechniques.

FIG. 2 depicts an example of conventional ARQ operation in which eachpacket is a MAC layer packet containing one or more ARQ blocks. MAClayer ARQ alone does not improve spectral efficiency. However, with itsretransmission mechanism to correct packet errors at the cost of extradelays, ARQ provides a more reliable link layer as seen by applications,and permits link adaptation for higher spectral efficiency. As can beseen in FIG. 2, there may be some inefficiency when an ACK is lost dueto error, and a correctly received packet is retransmitted.

Chase Combining HARQ in the PHY layer is supported to further improvethe reliability of a retransmission stored in a HARQ buffer by combiningone or more previous transmissions decoded in error. In HARQ ChaseCombining, all retransmissions sent include the same information and usethe original modulation-coding scheme (MCS). To streamline the HARQfeedback, a dedicated ACK channel is also provided on the transmissionside for purposes of HARQ ACK/NACK signaling, e.g. ACKCH channels 150a-150 n in FIG. 1.

In the case of WiMax (or other communication methodologies), the systemmay, from time to time, encounter communication channel conditions thatresult in or near complete packet reception, making the use of HARQ orother signaling protocols unnecessary, at least for a portion of thetime the communication channel is in use for a particular SF. In thissituation, the overhead associated with HARQ signaling (e.g., ACKCH 150a-150 n in FIG. 1) must still be allocated because, in conventionalsystems known to date that implement a HARQ signaling scheme, e.g.,WiMax, HARQ may only be enabled at the time a SF is established betweena BS and SS, and there is no method or system that solves the problem ofthe increased overhead and decreased data throughput when HARQ may notbe necessary for reliable communications.

Under the current WiMax standard, HARQ and associated parameters arespecified and negotiated using Station Basic Capability-Request/Response(SBCREQ/RSP) messages during network entry or re-entry procedure. Underthe Standard, a MS shall support per-connection based HARQ, and HARQ canbe enabled on a per Connection ID (CID) basis by using Dynamic ServiceAddition/Dynamic Service Change (DSA/DSC) messages.

HARQ may be enabled or disabled by setting the “ACK disable” bit. HARQis enabled if “ACK disable”=0, and is disabled otherwise, i.e. “ACKdisable”=1. The DL HARQ sub-burst Information Element (IE) defines the“ACK disable” bit setting. However, it may be difficult to determinewhether HARQ should be enabled or disabled during initial channel setup,and HARQ may not continue to be necessary if the communication channel'squality improves to an acceptable or desirable level.

A further problem with the current standards-based WiMAX implementationis that the HARQ Enable/Disable decision is fixed and static. Thedecision on HARQ Enable/Disable is made only when a Service Flow (SF) issetup. Once HARQ is enabled or disabled at the time the SF isestablished, the communication channel continues with the same HARQconfiguration, i.e., no change during SF, regardless of the relativechannel condition. Thus, even when channel quality is sufficient for aparticular QoS requirement without HARQ, HARQ will continue to be used,resulting in increased network overhead.

Thus, even though conventional HARQ often serves useful purposes, thereis a need for a system and method that are capable of enabling networkelements in a communication link to dynamically select HARQ processingafter a SF has been established to account for the availability of agood communication channel for which HARQ is not required at all times.

Further, the currently-implemented WiMAX implementation has difficultyin making a decision whether HARQ should be enabled or disabled when anew SF is setup since there generally is not enough information aboutthe channel condition for a new SF. Currently, WiMAX always configuresHARQ to be enabled in order to minimize the risk of low throughput onthe downlink (DL) with the cost of a UL resource for ACKCH. Moreover,the number of Acknowledgement Channels must be increased with the numberof users that are enabling HARQ, leading to decreased efficiency interms of bandwidth utilization and increased overhead.

While the current 802.16 WiMAX standard states that ACK disable bit isconfigurable to be either a “1” or “0”, the current implementation ofthe standard provides no guidance concerning when and under whatcircumstances the ACK disable bit should be set to either a “1” or “0”.As it currently is implemented, any mechanism may be applied, whichresults in various implementation issues for a large number ofstakeholders seeking to widely implement WiMAX.

What is needed for improved channel utilization and increased efficiencyin WiMAX networks is a dynamically selectable HARQ Enable/Disable schemethat uses information on changing channel conditions to determinewhether HARQ should continue to be enabled or disabled during an ongoingSF by selectively being able to set the “ACK disable” bit.

SUMMARY

The system and method of this disclosure provide various features,functions, and capabilities as discussed more fully in the detaileddescription, and as summarized below. For example, this disclosureprovides a novel and useful signaling method and system for use in acommunications link, with particular application in wirelesstelecommunication systems such as those adhering to IEEE 802.16 (WiMAX),3GPP, 3GPP2, etc. communication standard specifications that utilizeHARQ protocol mechanisms, but is not limited to use with these systems.

One major challenge in broadband wireless access networks is to providefast, reliable services to time-sensitive communications. Embodiments ofthis disclosure provide a dynamic HARQ scheme for wirelesscommunications systems which follows the multi-channel chase combiningHARQ adopted by WiMAX, for example, while enabling the base station (BS)to proactively react to poor channel conditions by selectivelyimplementing HARQ on a per burst or frame basis.

Various embodiments of this disclosure dynamically implement HARQ byenabling the BS to selectively enable or disable the use of HARQ after aSF has been established, thus reducing overhead and increasing datathroughput and/or the number of users that may access the communicationsnetwork.

In one or more embodiments, a Dynamic Enable/Disable system and methodare disclosed where HARQ is selectively Enabled or Disabled by an “ACKdisable” bit during a SF depending on channel condition. In thisdisclosure, “dynamic” means that HARQ is configurable to be enabled ordisabled on a “per burst” or per frame basis, which does not necessarilymean a “real time” change.

Various metrics may be used in making the initial and subsequentdecisions as to whether to enable or disable HARQ. For example, StandardDeviation (SD) of PCINR, or error rate r=NACK/(ACK+NACK) may be usedeither alone or in combination to aid in making a threshold decision onHARQ enablement.

In one embodiment, a method of increasing data throughput in a wirelesscommunications network over which a radio frequency (RF) signal istransmitted between a base station (BS) and one or more subscriberstations (SS) and/or mobile stations (MS) over a communications channelhaving a time-varying measure of quality includes establishing a serviceflow (SF) and initially enabling a hybrid automated repeat request(HARQ) protocol between the BS and the MS; determining, at a particulartime, the measure of quality of the communications channel; comparingthe determined measure of quality with a predetermined channel qualitythreshold; and selectively disabling the HARQ protocol based upon afirst comparison result while continuing the SF between the BS and MS.In one aspect of this embodiment, the method further includesdetermining, at a subsequent time, that the time-varying measure ofquality of the communications channel has deteriorated below thepredetermined channel quality threshold; and selectively reenabling theHARQ protocol in the established SF.

In another embodiment, a base station (BS) coupled to one or moresubscriber stations (SS) and/or mobile stations (MS) over a wirelessradio access network (RAN) includes a transceiver; a baseband processorcoupled to said transceiver; a hybrid automatic repeat request (HARQ)processor coupled to said baseband processor and which includes anACK/NACK processing module; a channel quality evaluation module; a HARQenable/disable controller operatively coupled to said ACK/NACKprocessing module and said channel quality evaluation module andoperative to selectively enable and/or disable a HARQ protocol within anestablished service flow (SF). In one aspect of this embodiment, if theHARQ protocol is enabled, the HARQ enable/disable controller isconfigured to compute a metric m comprising a ratio of a StandardDeviation (SD) of a Physical Carrier-to-Interference-Ratio (PCINR)reported by one of the one or more subscriber stations (SS) and/ormobile stations (MS) to a packet error rate r determined by the BS,wherein the metric m=SD/r, and r=NACK/(ACK+NACK); and responsive to afirst comparison result between the computed metric m and anoperator-selectable first threshold value, the HARQ enable/disablecontroller is further configured to selectively disable the HARQprotocol within the established service flow (SF). In a further aspectof this embodiment, if the HARQ protocol is disabled, the HARQenable/disable controller is configured to compare the SD to anoperator-selectable second threshold value and determine a secondcomparison result; and selectively reenable the HARQ protocol within theestablished service flow (SF) in response to the second comparisonresult.

In another embodiment, a computer-readable medium includes computerreadable code embodied therein which, when executed by a computer,causes the computer to carry out the functions of establishing a serviceflow (SF) and initially enabling a hybrid automated repeat request(HARQ) protocol between the BS and the MS; determining, at a particulartime, the measure of quality of the communications channel; comparingthe determined measure of quality with a predetermined channel qualitythreshold; selectively disabling the HARQ protocol based upon a firstcomparison result while continuing the SF between the BS and MS; afterselectively disabling the HARQ protocol, determining, at a subsequenttime, that the time-varying measure of quality of the communicationschannel has deteriorated below the predetermined channel qualitythreshold; and selectively reenabling the HARQ protocol in theestablished SF.

BRIEF DISCUSSION OF THE DRAWINGS

FIG. 1 provides a block diagram of a conventional wireless communicationsystem in which the system and method of this disclosure may beimplemented;

FIG. 2 provides an example of conventional MAC layer ARQ operation in awireless communications systems;

FIG. 3A provides a graphical representation of PCINR data for acommunications channel having a relatively high Standard Deviation overtime;

FIG. 3B provides a graphical representation of PCINR data for acommunications channel having a relatively low Standard Deviation overtime;

FIG. 4 illustrates a state diagram of HARQ ON/OFF states and theirtransitions for various channel conditions in one or more embodiments;

FIG. 5 illustrates a state transition condition for one or moreembodiments in which a decision rule is applied to improve networkperformance in terms of throughput and capacity;

FIG. 6 provides a flowchart of a method of an embodiment;

FIG. 7 provides a flowchart of a method of an embodiment; and

FIG. 8 provides a functional block diagram of a Base Stationillustrating a HARQ processing module of an embodiment.

DETAILED DESCRIPTION

In the discussion of various embodiments and aspects of the system andmethod of this disclosure, examples of MS/SS 130 may include any one ormore of, for instance, a personal computer, portable computer, personaldigital assistant (PDA), workstation, web-enabled mobile phone, WAPdevice, web-to-voice device, or other device. Those with skill in theart will appreciate that the inventive concept described herein may workwith various system configurations.

In addition, various embodiments of this disclosure may be made inhardware, firmware, software, or any suitable combination thereof.Aspects of this disclosure may also be implemented as instructionsstored on a machine-readable medium, which may be read and executed byone or more processors. A machine-readable medium may include anymechanism for storing or transmitting information in a form readable bya machine (e.g., a computing device). For example, a machine-readablestorage medium may include read only memory, random access memory,magnetic disk storage media, optical storage media, flash memorydevices, and others. Further, firmware, software, routines, orinstructions may be described herein in terms of specific exemplaryembodiments that may perform certain actions. However, it will beapparent that such descriptions are merely for convenience and that suchactions in fact result from computing devices, processors, controllers,or other devices executing the firmware, software, routines, orinstructions.

According to various embodiments, CQI Channels 160 a-160 n in FIG. 1 mayinclude a Standard Deviation of the channel condition informationdescribed above. In other words, MS/SS 130 n may report a StandardDeviation of channel condition information. Standard Deviation of thechannel condition information may indicate the combined effect ofDoppler and fading. For example, a higher PCINR Standard Deviation overa number of time points may indicate high Doppler and fast fadingeffects on the communication channel throughout the number of timepoints as compared to a lower PCINR Standard Deviation. Each time pointmay represent a transmission of a communication between BS 110 and MS/SS130 on a communication channel. A lower PCINR Standard Deviation mayindicate low Doppler and low fading effects throughout the number oftime points as compared to a higher PCINR Standard Deviation. Thus, thePCINR Standard Deviation, for example, may be used to indicate channelcondition of the communication channel throughout the number of timepoints. The number of time points observed by the MS/SS 130 in order togenerate the Standard Deviation may be configurable. In other words, avendor implementing the system or method may vary the number of timepoints used to generate the Standard Deviation. For example, the numberof time points may include all or a portion of the number of time pointssince communication on a communication channel is established between BS110 and MS/SS 130 n.

FIG. 3A is a two-dimensional graph illustrating an example of PCINR data308 a over time 304 exhibiting relatively high Standard Deviation abouta mathematical mean PCINR 306 a, according to an embodiment. PCINRvalues 302 are shown as a function of time 304. It should be understoodthat in FIG. 3A and any other figures illustrating a two-dimensionalgraph herein, the graphs are illustrative only and should not be viewedas limiting. For example, the axes may be reversed as appropriatewithout departing from the scope of this disclosure. As previouslynoted, a higher Standard Deviation of PCINR, for example, over a numberof time points may indicate high Doppler and fast fading effects of thecommunication channel as compared to a lower Standard Deviation.

FIG. 3B is a two-dimensional graph illustrating an example of PCINR data308 b over time 304 exhibiting relatively low PCINR Standard Deviationabout a mathematical mean PCINR 306 b, according to an embodiment. PCINRvalues 302 are shown as a function of time 304. As previously noted, alower PCINR Standard Deviation, for example, over a number time pointsmay indicate low Doppler and slow fading effects of the communicationchannel as compared to a higher PCINR Standard Deviation.

BS 110 may be configured to use the PCINR information from CQI Channels160 n to perform downlink adaption for a subsequent communication withMS/SS 130 n. In particular, if HARQ is not enabled, BS 110 mayselectively enable HARQ according to the Standard Deviation of PCINRreported by a particular MS/SS 130. Thus, channel condition informationbased on CQI or PCINR data may enhance the ability of BS 110 to select amore appropriate signaling scheme (i.e., to either selectively anddynamically enable or disable HARQ) for communications to reflectchanging channel conditions as compared to a static implementation ofHARQ-enabled or disabled.

According to various embodiments, HARQ ACKCH channels 150 n may includeanother type of channel stability information, such as, for example, anACK/NACK ratio. The ACK/NACK ratio indicates a ratio of successfultransmissions and non-successful transmissions, thereby indicatingchannel stability.

ACK/NACK feedback information provides useful information representing achannel condition and HARQ performance. During a certain time window, ifmost feedbacks are ACKs, then that implies that channel is good or HARQis working very well in unstable channel condition. The error rate r isdefined by r=NACK/(ACK+NACK). If r is relatively high, it implies thatthe channel is not good (e.g., unstable) or that HARQ, if enabled, isnot working well. If r is relatively low, it implies that the channel isgood or that HARQ is working very well with the unstable channelcondition.

Although both SD PCINR and error rate r provide useful information,synergy may be achieved by the use of these two parameters incombination as a measure of channel stability. In one or moreembodiments, a metric m combining SD PCINR with ACK/NACK feedback, i.e.,r, is defined as:

m=SD/r,

where SD is the Standard Deviation of PCINR and

r=NACK/(ACK+NACK).

If SD is relatively high and error rate r is relatively low such thatthe metric m is a relatively large number, the channel is unstable andthe error rate is low. In this situation, better overall systemperformance would be obtained by keeping HARQ enabled. However, if SD islow and the error rate r is high such that the metric m is small, thechannel is stable and the error rate is high, better system performancewould result by keeping HARQ disabled. Exemplary values for SD and r maybe SD=6.3 (i.e., 8 dB), and r=10%, such that m=6.3/0.1=63. Other valuesfor SD and r may be appropriate for different network requirements andconditions, as would be known to a person with ordinary skill in theart.

In various embodiments, HARQ is selectively and dynamically enabled ordisabled based on feedback information from MS/SS 130, i.e., SD of PCINRalone (if HARQ is disabled) and in combination with packet error rater=NACK/(ACK+NACK) (if HARQ is enabled), during a SF. HARQ enable (ON)and disable (OFF) are dynamically configured. HARQ ON/OFF states andtheir transitions are depicted in FIG. 4.

In FIG. 4, for the state where HARQ is “OFF”, and if the channel isstable, then no gain from HARQ would be expected. A stable channelimplies that the SD of PCINR is low or that the PCINR is increased. Whenthe channel becomes unstable, then a processing gain from enabling HARQwould be expected. This implies that SD of PCINR is high, i.e., PCINRhas high variability due to doppler or fading, for example, or thatPCINR has decreased.

For the state in FIG. 4 where HARQ is “ON”, a stable channel conditioncould also imply that the number of packet errors represented by thenumber of NACKs is low. An unstable channel condition implies that thenumber of packet errors represented by the number of NACKs is high.Standard Deviation of PCINR may represent channel fluctuation. If theStandard Deviation is relatively high, it implies that a channel is morefluctuating. If the Standard Deviation is low, it implies that a channelis relatively stable. In a relatively high fluctuating channelenvironment, HARQ could be more beneficial to achieve the target bursterror rate (1%) with lower CINR than required at the target error rate(1%), i.e., a high gain from the use of HARQ could be expected. In arelatively stable channel environment, HARQ gain may not be achieved orexpected as much in the case of an unstable channel condition.

Based on the rationale above, the state diagram of FIG. 5 can bedefined, where TH1 and TH2 are operator-selectable/configurablethresholds for metric m and SD, respectively. If HARQ is enabled, and ifmetric m>TH1, then HARQ should remain enabled. If, however, metricm<TH1, then HARQ should be turned off. Once HARQ is disabled, there areno “ACKS” or “NACKS” to determine the error rate r. Consequently, SDPCINR may be used to assess the channel stability/quality. If SD<TH2, orif the CQI has increased, then HARQ should remain disabled. However, ifSD>TH2, or if CQI is decreased, then the state should transition to HARQenabled. By applying the decision rules, the communications network canimprove throughput and capacity. It should be noted that the statetransition diagrams in FIGS. 4 and 5 are occurring during a previouslyestablished SF, contrary to conventional approaches which use HARQ in astatic and unchanging mode.

A flowchart of a method of an embodiment is provided in FIG. 6. Process600 starts at step 610, in which a service flow (SF) is establishedbetween the BS and a MS, for example. A HARQ signaling protocol isenabled at step 620. Thereafter, channel stability is determined at step630 by one or more techniques, as discussed above, e.g., SD PCINR, errorrate r, CQI, or metric m. A comparison is made between the currentmeasure of channel stability and an operator-selectable threshold atstep 640. If the channel is assessed as being stable, then the HARQprotocol is disabled at step 650, and the process returns to step 630 tore-determine channel stability. If, however, the channel is assessed asbeing unstable at step 640, then the process moves to re-enable HARQsignaling at step 660, after which the process returns to step 630 tore-determine channel stability.

A flowchart of a method of an embodiment is provided in FIG. 7. Process700 starts at step 710, in which a service flow (SF) is establishedbetween the BS and a MS, for example. A HARQ signaling protocol isenabled at step 720. Since HARQ is now enabled, ACKs and NACKs may bereceived in addition to channel quality information, which may be in theform of SD of PCINR. A stability metric m=SD/r is determined at step730, and the resultant metric m is compared to a firstoperator-selectable threshold value TH1 at step 740. If m>TH1, then theprocess continues by returning to step 730 to re-determine the stabilitymetric, m. If, however, m<TH1, then HARQ is disabled at step 750. SinceHARQ is disabled, ACKs and NACKs are no longer available to assesscommunications channel quality. So now, SD PCINR or CQI may be used atstep 760 for comparison to a second operator-selectable threshold TH2.If SD<TH2, then the process returns to step 750 with HARQ remainingdisabled until SD>TH2, after which the process returns to enable HARQ atstep 720.

In the embodiment of FIG. 8, a base station base station (BS) iscommunicatively coupled to one or more subscriber stations (SS) and/ormobile stations (MS) over a wireless radio access network (RAN). Thebase station includes transceiver 810 coupled to baseband processor 820.HARQ processor 830 is coupled to baseband processor 820. HARQ processor820 includes ACK/NACK processing module 831 that is configured toreceive and process ACKs and/or NACKs, and to determine a packet errorrate, for example. A channel quality evaluation module, e.g., SDPCINR/CQI evaluation module 833 is configured to evaluate indications ofchannel quality transmitted over CQI channels 160 n. HARQ enable/disablecontroller 835 is operatively coupled to ACK/NACK processing module 831and channel quality evaluation module 833, and operates to selectivelyenable and/or disable a HARQ protocol within an established service flow(SF) depending on evaluation of SD PCINR and/or packet error rate.Memory 837 may be available to one or more of the above modules forstoring data, including any operator-selectable threshold values.

SD PCINR/CQI evaluation module 833 may be configured to utilize SD PCINRthat represents communications channel fluctuation reported by one ofthe one or more SS and/or MS to determine a relative channel quality, orSD PCINR/CQI evaluation module 833 may utilize a channel qualityindication (CQI) reported by one of the one or more SS and/or MS.

ACK/NACK processing module 831 may be configured to determine a packeterror rate r, wherein r=NACK/(ACK+NACK). Further, if the HARQ protocolis enabled, HARQ enable/disable controller 835 may be configured tocompute the metric m described above. Further, responsive to a firstcomparison result between the computed metric m and anoperator-selectable first threshold value, HARQ enable/disablecontroller 835 may be further configured to selectively disable the HARQprotocol within the established SF.

If the HARQ protocol is disabled, the HARQ enable/disable controller 835may be configured to compare the SD to an operator-selectable secondthreshold value and to determine a second comparison result and,depending on the second comparison result, HARQ enable/disablecontroller 835 may selectively reenable the HARQ protocol within theestablished SF. In addition, the first and second operator-selectablethreshold values may be determined and selected based upon a desiredquality of service (QoS) for the established SF in the wireless radioaccess network.

In addition, base station 800 may also include a computer interfaceconfigured to allow a user to monitor system parameters and to inputselected threshold values into a memory associated with the HARQprocessor.

The various modules and interfaces described above can be implemented byany number of processors, memory, and input/output devices, as are knownin the art.

Various embodiments herein are described as including a particularfeature, structure, or characteristic, but every aspect or embodimentmay not necessarily include the particular feature, structure, orcharacteristic. Further, when a particular feature, structure, orcharacteristic is described in connection with an embodiment, it will beunderstood that such feature, structure, or characteristic may beincluded in connection with other embodiments, whether or not explicitlydescribed. Thus, various changes and modifications may be made to thisdisclosure without departing from the scope or spirit of the inventiveconcept described herein. As such, the specification and drawings shouldbe regarded as examples only, and the scope of the inventive concept tobe determined solely by the appended claims.

1.-21. (canceled)
 22. A method of increasing data throughput in awireless communications network over which a radio frequency (RF) signalis transmitted between a base station (BS) and a mobile station (MS)over a communications channel having a time-varying measure of quality,the method comprising: enabling a hybrid automated repeat request (HARQ)protocol between the BS and the MS, wherein a service flow (SF) isestablished between the BS and the MS; comparing the time-varyingmeasure of quality of the communications channel with a predeterminedchannel quality threshold, wherein the time-varying measure of qualityof the communications channel is determined based upon a statistic of aPhysical Carrier-to-Interference-Ratio (PCINR) reported by the MS; andselectively disabling the HARQ protocol based upon a comparison resultof said comparing operation while continuing the SF between the BS andMS.
 23. The method of claim 22, wherein the statistic comprises aStandard Deviation (SD) of the PCINR.
 24. The method of claim 23,wherein the time-varying measure of quality of the communicationschannel is determined further based upon a packet error rate rdetermined by the BS, wherein r=NACK/(ACK+NACK).
 25. The method of claim24, wherein the time-varying measure of quality of the communicationschannel is determined as a ratio of the SD of the PCINR and the packeterror rate r.
 26. The method of claim 22, wherein, after selectivelydisabling the HARQ protocol: determining that the time-varying measureof quality of the communications channel has deteriorated below thepredetermined channel quality threshold; and selectively reenabling theHARQ protocol in the established SF.
 27. The method of claim 26,wherein, after the HARQ protocol is selectively reenabled, maintainingthe HARQ protocol as enabled, based upon a determination that thetime-varying measure of quality of the communications channel isdetermined to be greater than an operator-selectable first thresholdvalue.
 28. The method of claim 22, wherein, after the HARQ protocol isselectively disabled, maintaining the HARQ protocol as disabled, basedupon a determination that the time-varying measure of quality of thecommunications channel is determined to be less than anoperator-selectable second threshold value.
 29. The method of claim 22,wherein the HARQ protocol is used in a WiMAX network implemented, atleast in part, under the IEEE Standard 802.16.
 30. A base station (BS)coupled to one or more subscriber stations (SS) and/or mobile stations(MS) over a wireless radio access network (RAN), the base stationcomprising: a transceiver; a baseband processor coupled to saidtransceiver; and a hybrid automatic repeat request (HARQ) processorcoupled to said baseband processor, said HARQ processor comprising: achannel quality evaluation module, wherein the channel qualityevaluation module is configured to utilize a Standard Deviation (SD) ofa Physical Carrier-to-Interference-Ratio (PCINR) reported by one of theone or more subscriber stations (SS) and/or mobile stations (MS) todetermine a relative channel quality; and a HARQ enable/disablecontroller operatively coupled to said channel quality evaluation moduleand configured to selectively enable and/or disable a HARQ protocolwithin an established service flow (SF).
 31. The base station of claim30, wherein said HARQ processor further comprises an ACK/NACK processingmodule configured to determine a packet error rate r, whereinr=NACK/(ACK+NACK).
 32. A non-transitory computer-readable storage mediumstoring computer readable code thereon which, when executed by acomputer, causes the computer to carry out operations related toincreasing data throughput in a wireless communications network overwhich a radio frequency (RF) signal is transmitted between a basestation (BS) and a mobile station (MS) over a communications channelhaving a time-varying measure of quality, the operations comprising:enabling a hybrid automated repeat request (HARQ) protocol between theBS and the MS, wherein a service flow (SF) is established between the BSand the MS; comparing the time-varying measure of quality of thecommunications channel with a predetermined channel quality threshold,wherein the time-varying measure of quality of the communicationschannel is determined based upon a statistic of a PhysicalCarrier-to-Interference-Ratio (PCINR) reported by the MS; andselectively disabling the HARQ protocol based upon a comparison resultof said comparing operation while continuing the SF between the BS andMS.
 33. The computer-readable storage medium of claim 32, wherein thestatistic comprises a Standard Deviation (SD) of the PCINR.